1. Field of the Invention
This invention relates to a gene encoding an enzyme aqualysin I, a recombinant vector comprising the gene and to Escherichia coli transformed with the recombinant vector, as well as to a process of producing aqualysin I utilizing the Escherichia coli transformant.
2. Description of the Related Art
Proteases are very important enzymes widely used as additives of detergents, catalyst for synthesizing peptides and as essential components of bioreactors. Aqualysin I is a heat-resistant alkalline protease having the optimum pH of about 10, which is produced by the optimum pH of about 10, which is produced by thermophilic bacterium Thermus aquaticus YT-1. Aqualysin I is very stable and is highly resistant to surfactants, so that it is used as an additive of detergents and as a component of bioreactors.
Aqualysin I is conventionally produced by separating the same from the supernatant of the culture of Thermus aquaticus YT-1. However, since the culturing temperature of Thermus aquaticus is as high as 65.degree. C., the culturing cost is high. Further, since the aqualysin I is purified from the supernatant of the culture, it is likely contaminated with an impurity existing in the culture. Still further, the productivity of aqualysin I by Thermus aquaticus YT-1 is not very high.
In order to solve the above-mentioned problems, it has been tried to produce aqualysin I employing a genetic engineering procedure by cutting out the aqualysin I gene from the genome of Thermus aquaticus YT-1, recombining the aqualysin I gene with a vector for Escherichia coli and expressing the aqualysin I gene in the Escherichia coli. However, aqualysin I is toxic to Escherichia coli, so that if the aqualysin I gene is expressed in an E. coli cell, the cell is killed. For this reason, aqualysin I has not yet been produced by genetic engineering processes.